1. Technical Field
The present invention relates to an optical device and a Mach-Zehnder interferometer that are used in a field of optical communication.
2. Related Art
In recent years, technologies for using Si as an optical waveguide material have been actively studied for the purpose of size reduction and massive production.
As one of this type of studies, it has been tried to form an optical device including a directional coupler and an optical waveguide connected to the directional coupler using an optical waveguide made of Si. For example, the following two documents are referred to.
“Silicon-wire-based ultrasmall lattice filters with wide free spectral ranges”, Koji Yamada, et. al., OPTICS LETTERS, Vol. 28, No. 18, pp 1663-1664
“Compact Wavelength-Selective Functions in Silicon-on-Insulator Photonic Wires”, Wim Bogaerts, et. al., IEEE Journal of selected topics in quantum electronics, Vol. 12, No. 6, pp 1394-1401
However, optical devices that are disclosed in the two Documents have large polarization dependency and can utilize only one of a TE polarization and a TM polarization. As a result, utilization efficiency of light is not sufficient.